Naraku had very likely already obtained Tessaiga's demon power.
If that were true, it would be truly terrifying.
Once Naraku found Dragon Man, whose demon power had reached the threshold of a great demon, whose abilities were exceptionally overbearing, and whose strength rivaled a great demon's, and absorbed him too, Naraku, with his "Cockroach Immortal Body" that could make up for his shortcomings in every area, would be powerful enough to attain godhood.
No one would be able to stop his advance.
That was what made Naraku with maxed-out Four Souls so terrifying.
Unlimited devouring!
Unlimited modification!
Unlimited evolution!
People said Naraku in the original timeline had grown powerful through the Shikon Jewel, but that was not quite true.
The Shikon Jewel was a catalyst, and the physical modifications at Mount Hakurei had indeed provided some help. Strictly speaking, however, Naraku had not truly fused with the Shikon Jewel until he transformed into the Super Hiten Giant Spider. Before that, the Shikon Jewel had remained in Naraku's possession, outside his body, without being absorbed.
The difference before and after absorption was enormous.
Before absorbing the Shikon Jewel, Naraku could completely ignore its will. After he absorbed it, the Jewel itself forced Naraku to make the wish that "one slash would unfailingly strike Kagome."
But in this timeline, Naraku had lost the vast majority of the Shikon Shards and could only seek another way forward.
As a result, he had stumbled onto a path that could not have been more correct.
That was to absorb the demon power of those demon swords.
The sentient souls of demon swords could not contend with Naraku's soul and will. The pressure Naraku faced on the level of the soul was practically negligible. Naturally, that allowed him to keep devouring without limit, with little to